1. Field of the Invention
This invention relates to electric power switches with an attachment having wiring leading out of the molded casing of the power switch. More particularly, it is directed to such a power switch having diverging through apertures in a wall of the molded casing of the switch through which the wiring of the attachment device is routed to relieve strain on the wiring imposed by an external pulling force applied to the wiring, and to preclude separation of the wiring from the attachment device, or application of an excessive force on the attachment device through the wiring.
2. Background Information
Electric power switches typically have one or more pole mechanisms each with a set of separable contacts opened and closed by the pole mechanism. Some electric power switches, such as circuit breakers, also have overcurrent protection provided by a trip unit or an overcurrent relay which automatically actuates the operating mechanism to open the separable contacts in response to an overcurrent condition. Other electric power switches, such as contacters for instance, may also have overcurrent protection.
For many applications, an electric power switch may be provided with one or more attachment devices which perform a variety of functions. For instance, a remotely operated power switch can have an attachment device in the form of a solenoid which when actuated, opens the power switch. Other attachment devices provide status information about the switch. Thus, an auxiliary switch reports the opened/closed condition of the switch. A bell alarm includes a switch which indicates, when actuated, that the trip unit of a switch provided with overcurrent protection has been actuated. It is now common to provide communications by which information may be exchanged between a switch and one or more other switches in a distribution system, and/or a remote station.
All of these attachment devices have wiring which extends from the molded casing in which they are mounted. The attachment devices can be mounted generally within the switch housing or casing, or in a separate compartment within the cover for the switch casing. They can also be enclosed within a separate housing mounted to the switch housing.
In some instances, the electrical leads on the attachment device are routed to an external terminal block associated with the switch which in turn connects the leads to external wiring. In other instances, the wiring leads directly from the attachment device to the other switch or remote station. In either case, it is undesirable to permit a pulling force applied to the electrical lead to bear directly on the connections of the wiring to the device. In fact, Underwriters Laboratories, which establishes standard for such devices, has established a pull-out test which requires that each auxiliary wire for an electrical switching device must support 20 pounds of weight for one minutes with the lead disconnected from the attachment device.
There is a need therefore, for an improved electric power switch having a simple, effective, and inexpensive arrangement for relieving strain on the electrical leads of attachment devices.
This need and others is satisfied by an electric power switch having a molded casing, a switch pole mechanism mounted in the molded casing and an attachment device having at least one electrical lead. The molded casing has a molded wall with a first face and a second face. At least first and second diverging through apertures extend through the casing wall from the first face to the second face. The at least one electrical lead is routed from the first face, through the first aperture, along the second face, and through the second through aperture back to the first face. The first and second through apertures diverge at an included angle of divergence of between about 40 and 80 degrees, but preferably at about 50 degrees. Preferably, these first and second through apertures diverge at substantially equal angles to an axis normal to the first face.
Where the attachment device has an additional electrical lead, the molded wall has diverging third and fourth through apertures extending through the casing molded wall section. The additional electrical lead is routed through a third through aperture to the second face, along the second face and back through the fourth aperture to the first face. These third and fourth through apertures are, respectively, parallel to the first and second through apertures.
In accordance with another aspect of the invention where the attachment device has multiple additional leads, the first and second through apertures form a first pair of through apertures which diverge in a first plane. The casing wall is provided with multiple additional pairs of diverging apertures extending from the first to the second face of the casing wall in multiple additional planes parallel to, and laterally spaced from, the first plane. Each multiple additional lead extends from the first face through one through aperture of an associated additional pair of through apertures to the second face, along the second face, and through the other through aperture of the associated additional pair of through apertures back to the second face.
In yet another aspect of the invention, each of the first and second diverging through apertures is widened to accommodate multiple electrical leads of the attachment. Thus, the first and second through apertures diverge in a first plane and extend in a lateral plane substantially perpendicular to this first plane. All of the multiple leads are routed from the first face through the first through aperture to the second face, along the second face and back through the second aperture to the first face.